Hero leveling during the first 2 weeks.

Alex, if you're going to talk about a "special tactic," please explain what it is.

It's usually difficult to break through gray fairies without losses, so the tactic is as follows.
Ideally, it's good if a Necromancer with skeletons and zombies arrives as the third hero in the tavern; then, take only undead troops and kill them. If there is no Necromancer, then you need to take 7 Goblins, divide them into groups of one, and eliminate the fairies with ranged attacks (usually there are 3-4 squads of them). Of course, you need to primarily kill and finish off entire stacks, as they can cast spells 2 times, and even 3-4 fairies can cast spells almost as well as 13 fairies.
For backup, you can take 1 stack of 3-4 Gargoyles.
The same applies to red archers, but there you will have to sacrifice either Gargoyles/Golems or take a weaker army, for example, Goblins and Centaurs from a Barbarian hero - it should be enough until you kill them with magic or block them with Gargoyles.